1) Tính nhanh :
a)-65.(87-17)-87.(17-65)
b)-215.[14+(-1236)]+215.(14-236)
2) Tìm x:
a)-(5x-13)-2(3x+1)=-4(x-8)-(-4)2
K
Khách
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Những câu hỏi liên quan
EG
4 tháng 2 2018
a)
(-12)(-13)+13(-22) = 12.13 - 13.22 = 13(12-22)=13.(-10)=-130
b) 15(-14) +15(-6) + (-20).25 = 15[(-14)+(-6)]+(-20).25=15.(-20)+(-20).25=(-20)(15+25)=-20.40=-800
c) -65.(87-17)-87(17-65) =
4 tháng 2 2018
a)(-12).(-13)+13.(-22)=12.13+13.(-22)=13.[12+(-22)]=13.(-10)=-130
b)15.(-14)+15.(-6)+(-20).25=15.[(-14)+(-6)]+(-20).25=15.(-20)+(-20).25=(-20).(15+25)=(-20).40=-800
c)-65.(87-17)-87.(17-65)=-65.87-(-65).17-87.17+87.65
=-65.87+65.17-87.17+87.65
=[(-65)+65].87+(65-87).17
=0.87+(-22).17
=0+(-374)=-374
LB
1
22 tháng 7 2023
2,
a) \(315-\left(135-x\right)=215\)
\(\Rightarrow135-x=315-215\)
\(\Rightarrow135-x=100\)
\(\Rightarrow x=135-100\)
\(\Rightarrow x=35\)
b) \(x-320:32=25\cdot16\)
\(\Rightarrow x-10=5^2\cdot4^2\)
\(\Rightarrow x-10=20^2\)
\(\Rightarrow x-10=400\)
\(\Rightarrow x=410\)
c) \(3\cdot x-2018:2=23\)
\(=3\cdot x-1009=23\)
\(\Rightarrow3\cdot x=1032\)
\(\Rightarrow x=1032:3\)
\(\Rightarrow x=344\)
d) \(280-9\cdot x-x=80\)
\(\Rightarrow280-x\cdot\left(9+1\right)=80\)
\(\Rightarrow280-10\cdot x=80\)
\(\Rightarrow10\cdot x=280-80\)
\(\Rightarrow10\cdot x=200\)
\(\Rightarrow x=20\)
e) \(38\cdot x-12\cdot x-x\cdot16=40\)
\(\Rightarrow x\cdot\left(38-12-16\right)=40\)
\(\Rightarrow x\cdot10=40\)
\(\Rightarrow x=40:10\)
\(\Rightarrow x=4\)
YN
22 tháng 11 2021
Answer:
Bài 1:
\(\left(135-35\right).\left(-37\right)+37.\left(-42-58\right)\)
\(=100.\left(-37\right)+37.\left(-100\right)\)
\(=\left(-3700\right)+\left(-3700\right)\)
\(=-7400\)
\(-65.\left(87-17\right)-87.\left(17-65\right)\)
\(=\left(-65\right).87-\left(-65\right).17-87.17+87.65\)
\(=-\left(-65\right).17-87.17\)
\(=17.\left(65-87\right)\)
\(=-374\)
\([3.\left(-2\right)-\left(-8\right)].\left(-7\right)-\left(-2\right).\left(-5\right)\)
\(=[\left(-6\right)+8].\left(-7\right)-\left(-2\right).\left(-5\right)\)
\(=2.\left(-7\right)-10\)
\(=-24\)
Bài 2:
\(\left(-55\right).\left(-25\right).\left(-8\right)\)
\(=\left(-55\right).[\left(-25\right).\left(-8\right)]\)
\(=\left(-55\right).200\)
\(=-11000\)
\(\left(-1\right).\left(-2\right).\left(-3\right).\left(-4\right).\left(-5\right).10\)
\(=[\left(-1\right).10].[\left(-2\right).\left(-5\right)].[\left(-3\right).\left(-4\right)]\)
\(=\left(-10\right).10.12\)
\(=-1200\)
a) -65 .( 87 - 17 ) -87 .( 17 - 65 )
= ( - 65 ) . 87 + 17 - 87 . 17 + 65
= { ( - 65 ) + 65 } . 87 + 17
= 0 . 87 + 17
= 17
b) -215 . [ 14 + ( -236 ) ] + 215 . ( 14 - 236 )
= -215 . 14 + ( - 236 ) + 215 . 14 - 236
= [ ( - 215 ) + 215 ] . 14 + { ( - 236 - 236 }
= 0 . 14 + 0
= 0